This invention relates generally to hydraulic fluid damped door closers and more particularly to fire resistant door closers incorporating features which discourage transfer of fire through a fire door.
Fire doors are designed to protect against passage of fire from one room to another in a building. In the U.S., the National Fire Protection Association promulgates construction and installation standards for fire doors and windows as a publication, NFPA 80. Listed fire doors are classified in twelve categories, and protection of an opening depends upon the use of a listed fire door, a listed frame, listed door hardware, and a listed door control device as specified under each door type. Fire classifications for buildings are specified in model building codes, government regulations, and state and local building codes. Fire door classifications are expressed in hourly ratings according to the Standard for Fire Tests of Door Assemblies--UL 10B, ANSI A2.2, ASTM E--152, CSFM 43.7, CAN4-S104 (ULC-S104), UBC 43-2-1991, and NFPA 252.
The classifications are determined by exposing the doors to fire testing under standard conditions, and hourly ratings indicate the duration of exposure which the door can withstand, such as 4, 3, 2, 11/2, 1, 3/4 hours, and 30 or 20 minutes. It is permissible to test a fire door with special hardware and installation. This is usually done by door manufacturers who wish to establish a fire rated door, frame, door control, and hardware combination which can be specified in a building contract. It should be noted that, although there are several very similar fire door assembly tests in use throughout the world, there is no single international fire test standard.
Generally, fire doors must be maintained closed and latched or must automatically close and latch under a broad range of fire exposure conditions in order to properly serve their fire protective function. Thus, the door control device must assure that the door closes after it has been opened, and the latch must maintain the door latched. Today, all fire door tests are performed without a door control device.
Most currently used door control devices employ hydraulic damping technology to control opening and closing speed of the door. The hydraulic fluid is commonly a petroleum based oil which is relatively inexpensive, plentiful, non-corrosive, and compatible with a wide range of metals and other materials. However, petroleum oils have an auto-ignition temperature ranging between approximately 500 and 750 degrees F. and may contribute to the spread of the fire, if exposed to high temperatures, even when the door control device is mounted on the non-fire side of the door.
Within a few minutes after a fire begins, assuming it is adjacent to a fire door, the temperature of the door control device on the non-fire side of the door begins to increase by conduction through the door. This causes the hydraulic fluid to expand, to leak around the seals of the door control device, and to run down the door. Approximately 10 to 15 minutes after the fire starts, the temperature on the non-fire side of the door is high enough to cause auto-ignition of the leaking fluid. Even though the door and frame assembly may have a fire rating of 2 hours, or more, the fire has transferred through the door in less than 15 minutes.
The foregoing illustrates limitations known to exist in present door control devices. It would be advantageous to provide an alternative directed to overcoming one or more of those limitations. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.